Abstract This project will examine the ability of ABP to predict cardiovascular morbidity, and represents a continuation of our work in two related areas. The first will be a continued follow-up of patients who have had ambulatory blood pressure monitoring (ABPM) performed by our group during the last 23 years, as well as clinic pressures, to establish the relative predictive value of different measures of BP for specific cardiovascular morbid events. The second will involve pooling comparable data from investigators in countries outside the US who have performed prospective ABPM studies and assessed cardiovascular morbid events, to increase the sample size, and thus increase the power to examine the predictive utility of ABPM for cardiovascular morbidity. This international collaborative project has already pooled data from 4 groups, with a total of 6,320 subjects, and will add data from 4 more. These combined data will include the bulk of the prospective studies on ABP performed throughout the world. The specific aims of Project 1 are: 1. To determine the cardiovascular prognosis of white coat hypertension (WCHT) in relation to normotension and sustained hypertension ; 2. To determine the cardiovascular prognosis of masked hypertension in relation to normotension and sustained hypertension; 3. To determine the prognostic significance of nocturnal dipping status and the morning surge of BP; 4. To determine the prognostic significance of blood pressure variability; 5. To determine the prognostic significance of ABP in African-Americans; 6. To compare the prognostic significance of ABP in populations with different risk factor profiles (Japanese vs. Europeans vs. Americans); and 7. To resolve discrepant findings from individual databases concerning ABP and prognosis.